The present invention relates to an image processing apparatus for masking an image.
Along with the development of solid-state image pickup devices in a variety of application fields, image processing has been performed using a pickup image. Although in a conventional endoscopic observation a fiber scope is used through which a doctor observes an optical image of the examined object through an eyepiece in order to diagnose the problem, an electronic scope incorporating a solid-state image pickup device such as a charge-coupled device (CCD) at the distal end of the endoscope has recently been used to monitor the image of an object through an external monitor. The doctor can then diagnose an object while observing its image on the monitor.
An example of such an electronic scope is described in Japanese Patent Disclosure (Kokai) No. 59-151591. Since the quality of the peripheral portion of the image produced by a solid-state image pickup device such as a CCD is poor, an optical aperture is formed in front of the device. The peripheral portion of the image is then masked and is not displayed on the screen. However, when an optical aperture is formed in front of the solid-state image pickup device, the peripheral image portion is distorted due to diffraction, a boundary between the masked and nonmasked image portions is blurred, and a displayed image cannot be clearly observed. As a result, the effect of masking is degraded.
In addition, in order to change the shape of the aperture when the optical aperture is used, it must be completely replaced with another one, with the accompanying difficulties.